witch Profilux do you have?
They are a little diffrent in the Ports.
You will find the most information about the ports in this dokument
https://www.aquariumcomputer.com/de/...ungsanleitung/
I dont know anything about clamp diods so i woud youse a 10K Resistor to pull the switch chanels to ground during they are open.

I woult try to connect the Switch channels of the S Port do the Bord and to a 10K Resister connetet to Ground.
Additional the Ground of the S Port to the Ground of your Bord and a additional 12 V source to * - - of the Port.

Without any Warenty god luck.